Adaptive antenna radio communication device

ABSTRACT

A device for estimating a direction-of-arrival of a radio wave, the device comprising an array antenna including a plurality of antenna elements for receiving a high frequency signal, a demultiplexer for demultiplexing the received high frequency signal for each of the plurality of antenna elements to generate a plurality of frequency component signals and a direction estimating unit for estimating the direction-of-arrival of the radio wave by using two or more of the plurality of frequency component signals which are contiguous in a frequency direction.

This application is a Continuation of U.S. patent application Ser. No.11/961,340, filed Dec. 20, 2007, which is a Divisional of U.S. patentapplication Ser. No. 10/524,253, filed Feb. 10, 2005, which is a U.S.National Phase Application of PCT International ApplicationPCT/JP2003/012346, the entire disclosure of which is incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to an adaptive antenna radio communicationdevice provided with a direction estimating unit of arrival paths and anarray antenna having a directivity controlling unit based thereon for adigital radio communication system in a multi-carrier transmissionmethod using a plurality of sub-carriers having different frequencies.

BACKGROUND ART

Signals received by a radio communication device have been interfered byvarious signals, leading to the deterioration of the reception quality.As a technique to suppress this kind of interference and stronglyreceive only signals arriving from a desired direction, an adaptivearray antenna (adaptive antenna) has been known. The adaptive arrayantenna can receive only signals arriving from a desired direction byadjusting a weight coefficient by which the receiving signals aremultiplied (hereinafter, the weight coefficient is referred to as“weight”) to adjust the amplitude and phase given for receiving signals.

Furthermore, demands for the mass radio communication and high speedhave been recently increased. To realize such demands, anti-multi-pathproperty and anti-fading countermeasure have been big subjects to besolved. One of approaches to solve the subjects is multi-carriertransmission transmitting in parallel by a plurality of narrowbandsub-carriers in a band for performing wideband transmission. Inparticular, the orthogonal frequency division multiplexing (OFDM)transmission method has been adopted in terrestrial digital broadcastingor wideband radio access systems.

When an adaptive array antenna is used in a multi-carrier transmissionsystem, both can be further characterized, thus enhancinganti-multi-path property and anti-fading property.

Description of detailed configuration will not be described. However, ina multi-carrier transmission system, there has been described aconventional radio device equipped with an adaptive array antenna, forexample, in JP-A-1999-205026. Due to this, even when the relative band(the ratio of the entire communication band in use to the centerfrequency of the entire communication band) was high, a directional beamof an antenna that is uniform at the entire communication bands in theOFDM transmission method can be obtained and transmission/reception thatis hard to be influenced by interfering wave such as multi-path and thelike in the entire communication band can be made, by calculating aweight of an antenna in the respective sub-carriers.

However, the conventional adaptive antenna radio communication devicehas a problem in that it was unable to estimate the direction withsufficient accuracy for receiving sub-carriers having low receivedpower, when it was influenced by frequency selective fading forperforming the direction estimation for each sub-carrier and calculatinga weight of a receive array. Furthermore, it has a problem in that, whenthe number of sub-carriers was high, the circuit specification hasincreased.

SUMMARY OF THE INVENTION

A device for estimating a direction-of-arrival of a radio wave, thedevice comprising an array antenna including a plurality of antennaelements for receiving a high frequency signal, a demultiplexer fordemultiplexing the received high frequency signal for each of theplurality of antenna elements to generate a plurality of frequencycomponent signals and a direction estimating unit for estimating thedirection-of-arrival of the radio wave by using two or more of theplurality of frequency component signals which are contiguous in afrequency direction.

DISCLOSURE OF THE INVENTION

The present invention estimates the average direction-of-arrival ofsub-carrier signals belonging to a divided band to which thecommunication band is divided, using a sub-carrier signal having highcorrelation of spatial spectrum among adjacent sub-carrier signals in awideband multi-carrier transmission method. So, even when sub-carriershaving low received power exist, the deterioration estimation degree canbe suppressed by estimating the direction-of-arrival as sub-carriersignals including such sub-carriers. Also, individual or averagedirection of a plurality of paths for the respective sub-carriers can beestimated.

In case of directivity transmission, an angle spread based on a spatialspectrum is detected in the respective divided bands or the entirecommunication band. When the angle spread is small, a transmissiondirectivity control is performed on the basis of the averagedirection-of-arrival of the entire sub-carrier signals. On the otherhand, when the angle spread is large, a directivity transmission controlis performed either 1) in the direction giving the maximum receivedpower among the direction estimation results in the respective dividedbands or 2) in the direction giving the upper received power having thepredetermined number among the direction estimation results in therespective divided bands. Thus, a directivity transmission can be madein the direction of arrival path upon reception and interference withother users can be effectively reduced, thus enhancing the communicationquality and improving the system capacity.

An adaptive antenna radio communication device according to the presentinvention comprises an array antenna made up of a plurality of antennaelements receiving high frequency signals that are transmitted bymulti-carrier; a demultiplexer for demultiplexing the signal received bythe respective antenna elements to a plurality of sub-carrier signals;Nd divided band direction estimating units for estimating thedirection-of-arrival of a radio wave by dividing the entirecommunication band being multi-carrier transmitted into Nd bands(however, Nd is 2 or more or a positive integer less than the number ofsub-carriers used being multi-carrier transmitted) and using sub-carriersignals belonging to the respective divided bands; a divided band arrayweight creating unit for creating a weight of a receive array having adirectional beam in the direction of estimation by the divided banddirection estimating unit for the respective divided bands; asub-carrier directivity creating unit for creating a directivity bymultiplication-combining the receive array weight created in eachdivided band with the corresponding sub-carrier signal belonging to thedivided band; and a demodulating unit for demodulating data by using theoutput of the sub-carrier directivity creating unit. Accordingly, sincethe direction-of-arrival of the sub-carrier signals in the divided bandcan be estimated, a directivity reception can be made on the basis ofthe direction estimation results.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also calculatespilot signal correlation values with the respective input sub-carriersignals using a known pilot signal embedded in a sub-carrier signal, andestimates the direction-of-arrival based on the correlation values ofsaid pilot signal correlation values calculated between the samesub-carrier signals received by different antenna elements. Thus, thedirection can be estimated on the basis of the phase of the pilotcorrelation values.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using correlation matrices integratingcorrelation matrices of the respective sub-carriers belonging to thesub-carrier signals.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation matrix R expressed asR=V₁V₁ ^(H)+V₂V₂ ^(H)+ . . . +V_(L)V_(L) ^(H) where L is the number ofsub-carriers belonging to the sub-carrier signals; Vk is a column vectorhaving a pilot signal correlation value as an m-th element in the m-thantenna element with respect to the k-th sub-carrier signal; and H is acomplex conjugate transposed operator. Accordingly, the averagedirection of the directions-of-arrival of the sub-carrier signals can bedetected with better accuracy.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival by using a correlation vector integratingcorrelation vectors of the respective sub-carriers belonging to thesub-carrier signals.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation vector z expressed asz=V _(1X) *V ₁ +V _(2X) *V ₂ + . . . +V _(LX) *V _(L)where L is the number of sub-carriers belonging to the sub-carriersignals; Vk is a column vector having a pilot signal correlation valueas an m-th element in the m-th antenna element with respect to the k-thsub-carrier signal; Vkx is an x-th element of the column vector Vk(however, x is a positive integer less than the number of antennaelements); and * is a complex conjugate operator. Thus, the averagedirection of the directions-of-arrival of the sub-carrier signals can bedetected with better accuracy.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also has a pathsearch unit for calculating a delay profile by calculating a crosscorrelation between respective input sub-carrier signals using a knownpilot signal embedded in the sub-carrier signal and detecting aplurality of path arrival timings from the delay profile, and estimatesthe direction-of-arrival based on the correlation value of the pilotsignal correlation value calculated between the same sub-carrier signalsreceived by different antenna elements in the respective path arrivaltimings. Thus, the direction-of-arrival of multi-path waves included inthe respective sub-carrier signals can be estimated.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation matrix integratingcorrelation matrices of the respective sub-carriers detected in therespective sub-carriers belonging to the sub-carrier signals.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation matrix R expressed as

$R = {\sum\limits_{k = 1}^{L}{\sum\limits_{p = 1}^{S}{{V_{k}(p)}{V_{k}(p)}^{H}}}}$where L is the number of sub-carriers belonging to the sub-carriersignals; Vk(p) is a column vector having the pilot signal correlationvalues as an m-th element in the m-th antenna element of the p-tharrival path (the number of whole arrival paths is specified as S) withrespect to the k-th sub-carrier signal; and H is a complex conjugatetransposed operator. Accordingly, the directions of arrival ofmulti-path waves included in the respective sub-carrier signals can beestimated with better accuracy.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation vector integratingcorrelation vectors of the respective sub-carriers detected in therespective sub-carriers belonging to the sub-carrier signals.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival using a correlation vector z expressed as

$z = {\sum\limits_{k = 1}^{L}{\sum\limits_{p = 1}^{S}{{V_{kx}(p)}*{V_{k}(p)}}}}$where L is the number of sub-carriers belonging to the sub-carriersignals; Vk(p) is a column vector having the pilot signal correlationvalues as an m-th element in the m-th antenna element of the p-tharrival path (the number of whole arrival paths is specified as S) withrespect to the k-th sub-carrier signal and * is a complex conjugateoperator. Thus, the directions of arrival of multi-path waves includedin the respective sub-carrier signals can be estimated with betteraccuracy.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also estimatesthe direction-of-arrival by any one of the MUSIC method, ESPRIT method,CAPON method and Fourier method using the correlation matrix R. Thus,various estimation methods of direction-of-arrival can be applied.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also has aspatial smoothing processing unit for performing spatial smoothingprocessing on said correlation matrix R and estimates thedirection-of-arrival by using any one of the MUSIC method, ESPRITmethod, CAPON method and Fourier method to the output from the spatialsmoothing processing unit. Thus, even when correlation waves exist, theaccuracy of estimation can be ensured.

The divided band direction estimating unit of the adaptive antenna radiocommunication device according to the present invention also has aunitary converting unit for performing unitary conversion processing onthe correlation matrix R and estimates the direction-of-arrival by usingany one of the MUSIC method, ESPRIT method, CAPON method and Fouriermethod to the output from the unitary converting unit. Thus, when anarray antenna is a uniform linear array, a directional vector is putinto a real number so that a throughput of operation can be reduced.

Furthermore, an adaptive antenna radio communication device according tothe present invention comprises an array antenna made up of a pluralityof antenna elements receiving high frequency signals that aretransmitted by multi-carrier; a demultiplexer for demultiplexing thesignal received by the respective antenna elements to a plurality ofsub-carrier signals; an entire band direction estimating unit forestimating the direction-of-arrival using multi-carrier signals in theentire communication band being multi-carrier transmitted; Nd dividedband direction estimating units for dividing the entire communicationband into Nd bands (however, Nd is 2 or more, or a positive integer lessthan the number of sub-carriers used being multi-carrier transmitted)and estimating the direction-of-arrival of a radio wave by usingsub-carrier signals belonging to the respective divided bands; adirection estimation result selecting unit for selecting and outputtingan estimation value of the entire band direction estimating unit whenthe deviation of the direction estimation results in ND divided banddirection estimating units is less than the predetermined value, and foroutputting an estimation value of the divided band direction estimatingunit when the deviation is greater than the predetermined value; and adivided band array weight creating unit for creating a weight of areceive array having a directional beam in the direction of estimationusing the output of the direction estimation result selecting unit.Accordingly, directivity control methods can be adaptively switched fromthe spread of the direction-of-arrival in a band.

Furthermore, an adaptive antenna radio communication device according tothe present invention comprises an array antenna made up of a pluralityof antenna elements receiving high frequency signals that aretransmitted by multi-carrier; a demultiplexer for demultiplexing thesignal received by the respective antenna elements to a plurality ofsub-carrier signals; an entire band direction estimating unit forestimating the direction-of-arrival using multi-carrier signals in theentire communication band being multi-carrier transmitted; Nd dividedband direction estimating units for estimating the direction-of-arrivalof a radio wave by dividing the entire communication band beingmulti-carrier transmitted into Nd bands (however, Nd is 2 or more, or apositive integer less than the number of sub-carriers used beingmulti-carrier transmitted) and using sub-carrier signals belonging tothe respective divided bands; a direction estimation result selectingunit for detecting an angle spread from the spatial profile calculatedin the entire band direction estimating unit, for selecting andoutputting an estimation value of the entire band direction estimatingunit when the angle spread is less than the predetermined value, oroutputting an estimation value of the divided band direction estimatingunit when the angle spread is greater than the predetermined value; anda divided band array weight creating unit for creating a weight of areceive array using the output of the direction estimation resultselecting unit. Accordingly, directivity control methods can beadaptively switched from the spread of the direction-of-arrival in aband.

Furthermore, the adaptive antenna radio communication device accordingto the present invention, in a radio system being multi-carriertransmitted in a time division duplex (TDD) method or a frequencydivision duplex (FDD) method, further comprises a sub-carriertransmission weight creating unit for calculating a weight of atransmission array that forms a transmitting directional beam in therespective divided bands based on the estimated direction resultselected by the direction estimation result selecting unit; and asub-carrier transmission directivity creating unit for transmitting adirectional beam being multiplied the transmitting sub-carrier signal bythe transmission array weight in the respective divided bands.Accordingly, directivity control methods can be adaptively switched fromthe spread of the direction-of-arrival in a band.

Furthermore, the adaptive antenna radio communication device accordingto the present invention, in a radio system being multi-carriertransmitted in a time division duplex (TDD) method, further comprises asub-carrier transmission weight creating unit using a weight of areceive array created in the divided band array weight creating unit foreach divided band as a weight of a transmission array; and a sub-carriertransmission directivity creating unit for transmitting a directionalbeam using a weight of a transmission array common to the respectivedivided bands. Thus, the same directivity as a receive directivity inthe respective divided bands can be used for transmitting.

Furthermore, the adaptive antenna radio communication device accordingto the present invention, in a radio system being multi-carriertransmitted in a time division duplex (TDD) method or a frequencydivision duplex (FDD) method, further comprises a sub-carriertransmission weight creating unit for calculating a weight of atransmission array in order to create a transmitting directional beam inthe direction of estimation giving maximum received power among thedirections of estimation by all divided band direction estimating units;and a sub-carrier transmission directivity creating unit fortransmitting a directional beam common to the entire divided band usingthe transmission array weight. Thus, a transmitting beam can be formedin the direction of path giving the maximum received power among thedivided bands.

Furthermore, the adaptive antenna radio communication device accordingto the present invention, in a radio system being multi-carriertransmitted in a time division duplex (TDD) method or a frequencydivision duplex (FDD) method, further comprises a sub-carriertransmission weight creating unit for calculating a deviation of theestimation direction outputted from the divided band directionestimating unit, calculating a weight of a transmission array forcreating a transmitting directional beam in the average direction ofdirection estimation values outputted from all divided band directionestimating units when the deviation is less than the predeterminedvalue, or calculating the transmission array weight in the direction ofestimation giving a predetermined number of the upper received poweramong all divided bands when the deviation is greater than thepredetermined value. Thus, directivity control methods can be adaptivelyswitched from the spread of the direction-of-arrival in a band.

Furthermore, in an adaptive antenna radio communication device accordingto the present invention, sub-carrier signals to which orthogonalfrequency division multiplexing (OFDM) is applied are used formulti-carrier transmission. So, multi-carrier can be transmitted in amodulation method having high frequency utilization efficiency.

Furthermore, in an adaptive antenna radio communication device accordingto the present invention, sub-carrier signals in which users aremultiplexed are used for the multi-carrier transmission by code divisionin the direction of frequency axis or time axis. Thus, the presentinvention has an action that can be applied to a system in which usermultiplexing can be made in accordance with code division.

The adaptive antenna radio communication device according to the presentinvention also creates a weight of a transmission array or a weight of areceive array for the respective multiplexed users for directionalreceiving. Thus, an optimum directivity can be controlled in therespective divided bands for the respective multi-users.

The divided band array weight creating unit of the adaptive antennaradio communication device according to the present invention also has adirectional beam in the direction estimation result of the divided banddirection estimating unit in its divided band and creates a weight of areceive array for creating a null in the estimation direction of othermultiplexed users. So, an optimum directivity can be received such thata null is formed in the direction of interference in the respectivedivided bands for the respective multi-users.

The sub-carrier transmission weight creating unit of the adaptiveantenna radio communication device according to the present inventionalso has a directional beam in the direction of a desired user andcreates a weight of a transmission array for creating a null in thedirection of other multiplexed users. Thus, an optimum directivity canbe transmitted/received such that a null is formed in the direction ofinterference in the respective divided bands for the respectivemulti-users.

According to the present invention, as described above, even when anadaptive antenna radio communication device equipped with an arrayantenna employs a wideband multi-carrier transmission method andsub-carriers having low received power exit, the deterioration of theestimation accuracy can be suppressed and the reception quality can beimproved. Furthermore, in case of a directivity transmission, multiuserinterference can be reduced and an improvement of the communicationquality can be devised.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a radiocommunication device in a first embodiment of the present invention;

FIG. 2 is a block diagram illustrating a detailed configuration of adivided band direction estimating unit in a first embodiment of thepresent invention;

FIG. 3 is a diagram illustrating the spatial profile calculation resultsfrom a divided band direction estimating unit in a first embodiment ofthe present invention;

FIG. 4 is a block diagram illustrating another configuration of adivided band direction estimating unit in a first embodiment of thepresent invention;

FIG. 5 is a block diagram illustrating a configuration of a radiocommunication device in a second embodiment of the present invention;

FIG. 6 is a block diagram illustrating a configuration of a radiocommunication device in a third embodiment of the present invention; and

FIG. 7 is a block diagram illustrating a configuration of a radiocommunication device in a fourth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are demonstrated hereinafter withreference to the drawings. Throughout the drawing, the same blocks whenshown in more than one figure are designated by the same referencenumerals.

1st Exemplary Embodiment

FIG. 1 is a block diagram illustrating a configuration of an adaptiveantenna radio communication device in a first embodiment of the presentinvention. The adaptive antenna radio communication device illustratedin FIG. 1 comprises an array antenna 1 made up of multiple Na antennaelements 1-1 to 1-Na; a demultiplexer 2-k (however, k is 1 to Na) fordemultiplexing a signal s1-k received by a k-th antenna element 1-k to aplurality of Ns sub-carrier signals fl-k to Ns-k after the highfrequency signal is frequency-converted; a divided band directionestimating unit 4-m for estimating the direction-of arrival usingsub-carrier signals belonging to the m-th divided band 3-m among dividedbands in which a communication band is divided into Nd bands; a dividedband array weight creating section 5-m for creating a weight of areceive array based on the direction estimation result from the m-thdivided band direction estimating unit 4-m; a sub-carrier directivitycreating unit 6-m for creating a directivity to sub-carrier signalsbelonging to the m-th divided band 3-m using the receive array weightcreated in the divided band array weight creating unit 5-m; and ademodulating unit 7 for demodulating data using each sub-carrier signalin which a directivity is received. Here, m indicates 1 to Nd.Incidentally, an example of a configuration is illustrated in FIG. 1when the number of antenna elements Na is 2, the number of sub-carriersNs is 4, and the number of divided bands Nd is 2.

The operation of the outline is described below with reference toFIG. 1. First, antenna elements 1-1 to 1-Na configuring the antennaelement 1 receives high frequency signals s1-1 to s1-Na respectivelythat is transmitted in a multi-carrier method. Of such signals, a highfrequency signal s1-k received by the k-th antenna element 1-k performsa high frequency amplification and frequency conversion sequentially inthe demultiplexer 2-k. A plurality of Ns sub-carrier signals f1-k, f2-k,. . . , fNs-k are extracted, which are used for multi-carriertransmission. Herein, an entire communication band of a receive signalcan be divided into Nd divided bands. Sub-carrier signals belonging tothe m-th divided band 3-m therein is input to the divided band directionestimating unit 4-m and the sub-carrier directivity creating unit 6-mrespectively. Incidentally, the number of divided bands Nd can be apositive integer within a range of the number of all Nssub-carriers≧Nd>1. Also, the number of sub-carriers belonging tosub-carrier signals belonging to each divided band 3 needs not to becertainly equal. The number of sub-carriers Nc (=Ns/Nd) is described tobe the same below.

Next, using sub-carrier signals belonging to the m-th divided band 3-m,the divided band direction estimating unit 4-m conducts estimation ofthe direction-of-arrival. FIG. 2 illustrates a detailed configuration ofthe divided band direction estimating unit 4.

In FIG. 2, a divided band direction estimating unit 4-1 is made up of apilot signal creating unit 20 for creating a pilot signal, i.e., a knownpilot signal embedded in each sub-carrier signal; a pilot signalcorrelation calculating unit 21 for calculating correlation valuesbetween each received sub-carrier signal and a created pilot signal; acorrelation matrix creating unit 22 for creating a correlation matrixbased on pilot signal correlation values; and a spatial profilecalculating unit 23 for calculating a spatial profile based on acorrelation matrix. Also, sub-carrier signals s21 received by theantenna element 1-1 and sub-carrier signals s22 received by the antennaelement 1-2 are input to the different pilot signal correlationcalculating unit 21 from the respective sub-carriers. The operation ofthe outline is described below with reference to FIG. 2. Incidentally,FIG. 2 illustrates an example of the divided band direction estimatingunit 4-1 in a first divided band 3-1 when the number of antenna elementsNa is 2 and the number of sub-carriers Nc in a divided band is 2.

The pilot signal creating unit 20 creates a known signal (hereinafterreferred to as a pilot signal) embedded previously in a sub-carriersignal. The pilot signal correlation calculating unit 21 performs acorrelation operation between created pilot signals and receiving pilotsymbols of the sub-carrier signals. Herein, a pilot signal is specifiedas r(s). However, s is 1 to Np where Np is the number of pilot signalsymbols.

A pilot signal correlation calculating unit 21-n-k performs acorrelation operation shown in the formula 1 for the n-th sub-carriersignal fn-k (t0) (incidentally, t0 represents a path arrival timing)belonging to the m-th divided band 3-m received by the k-th antennaelement 1-k. However, No is the number of over-samples for a symboland * indicates a complex conjugate. The pilot correlation value h nk iscalculated for sub-carrier signals (n=1˜Nc) belonging to the m-thdivided band 3-m received by all antenna elements (k=1˜Na).

$\begin{matrix}{h_{nk} = {\sum\limits_{s = 1}^{N_{p}}{{f_{n - k}\left( {t + {N_{0} \cdot \left( {s - 1} \right)}} \right)}{r^{*}(s)}}}} & (1)\end{matrix}$

The correlation matrix creating unit 22 calculates a correlation matrixR shown in the formula 3 using the pilot correlation value h nkcalculated in the pilot signal correlation calculating unit 21 and acorrelation vector Vn shown in the formula 2. However, n is 1 to Ns, kis 1 to Na and T is a vector transpose.

$\begin{matrix}{V_{n} = \begin{bmatrix}h_{n,1} & h_{n,2} & \ldots & h_{n,{Na}}\end{bmatrix}^{T}} & (2) \\{R = {\sum\limits_{n = 1}^{Nc}{V_{n}V_{n}^{H}}}} & (3)\end{matrix}$

The spatial profile calculating unit 23 performs the directionestimation using a correlation matrix R created in the correlationmatrix creating unit 22. Many direction estimation algorithms have beenproposed. However, below is described a case where an algorithm forcreating a spatial profile based on the Fourier method and detecting itspeak direction for finding a direction-of-arrival estimation value isapplied.

The spatial profile calculating unit 23 calculates a spatial profile byvarying a parameter (of a direction-of-arrival estimation evaluationfunction F(( ) shown in the formula 4 in a predetermined angle step Δ(.So it detects the peak direction having the predetermined number M (M□EMBED Equation. 3 □□□1) in the descending order of the peak level of aspatial profile and specifies it as a direction-of-arrival estimationvalue. However, a(( ) is a directional vector that depends on theelement arrangement of the array antenna 1. For example, it can beexpressed as the formula 5 for a uniform linear array having an elementspace d. Herein, ( is a wavelength of a center frequency in the dividedband 3-m in a carrier band, and ( specifies the normal direction of thelinear array as the direction of 0(. Furthermore, H is a complexconjugate transpose.

$\begin{matrix}{{F(\theta)} = {{a(\theta)}^{H}{{Ra}(\theta)}}} & (4) \\{{a(\theta)} = \begin{bmatrix}1 \\{\exp\left\{ {{- {j2\pi}}\;{d \cdot 1 \cdot \sin}\;{\theta/\lambda}} \right\}} \\\vdots \\{\exp\left\{ {{- {j2\pi}}\;{d \cdot \left( {{Na} - 1} \right) \cdot \sin}\;{\theta/\lambda}} \right\}}\end{bmatrix}} & (5)\end{matrix}$

FIG. 3 shows the spatial profile calculation result when the number ofarray elements Na is 8 and the number of sub-carriers Nc of sub-carriersignals is 2. FIG. 3A is the result when the angle of arrival of asub-carrier 1 θ1 is 20° and that of a sub-carrier 2 θ2 is −20°, whileFIG. 3B is the result when the angle of arrival of the sub-carrier 1 θ1is 5° and that of the sub-carrier 2 θ2 is −5°. As illustrated in FIG.3A, a beam former method is used for the direction-of-arrival estimationshown in the formula 4. When the arrival path intervals are separatedmore sufficiently than the beam width of the array antenna 1, the peakfor each path direction can be detected. Furthermore, as shown in FIG.3B, a plurality of angles of arrival of paths are close to one afteranother, a spatial profile having the smaller number of peaks than thenumber of paths is obtained. The peak direction in this case is steeringthe direction in which the composite power of multiple paths ismaximized.

Then, the divided band array weight creating unit 5-m creates a weightof a receive array facing toward the main beam in the maximum peakdirection of the direction estimation result in the divided banddirection estimating unit 4-m or in the multiple peak directions of thepredetermined number for sub-carrier signals belonging to the m-thdivided band 3-m.

Next, the sub-carrier directivity creating unit 6-mmultiplication-combines commonly each sub-carrier signal by the createdreceive array weight and outputs it to the demodulating unit 7.Incidentally, the receive array weight is created in consideration of awavelength λm of a center frequency of each divided band 3-m in a radiofrequency band. This is effective particularly when the relative band ishigh. For example, the receive array weight Wm in the m-th divided band3-m can be expressed as the formula 6 for a uniform linear array havingan element space d. Herein, θ0 is the direction estimation result.Incidentally, the normal direction of the linear array is specified asthe direction of 0°.

$\begin{matrix}{W_{m} = \begin{bmatrix}1 \\{\exp\left\{ {{j2\pi}\;{d \cdot 1 \cdot \sin}\;{\theta_{0}/\lambda_{m}}} \right\}} \\\vdots \\{\exp\left\{ {{- {j2\pi}}\;{d \cdot \left( {{Na} - 1} \right) \cdot \sin}\;{\theta_{0}/\lambda_{m}}} \right\}}\end{bmatrix}} & (6)\end{matrix}$

Next, the demodulating unit 7 performs a demodulation operation usingeach sub-carrier signal in which a directivity is received from thesub-carrier directivity creating unit 6 via all divided band 3.

In this embodiment, a correlation vector Vn is obtained from eachsub-carrier signal belonging to sub-carrier signals belonging to thedivided band 3, which is then synthesized to create a correlation matrixR. By performing a direction-of-arrival estimation using the correlationmatrix, the average direction-of-arrival of sub-carrier signals in adivided band can be estimated. Accordingly, when the frequency intervalsbetween sub-carrier signals are sufficiently narrow, spatial correlationcharacteristics between adjacent sub-carrier signals become relativelyhigh. For this reason, even if a received power adjacent to thesub-carrier signal is low, the accuracy of direction-of-arrivalestimation can be ensured by performing the direction estimation aftercombining a plurality of the sub-carrier signals. When the frequencyintervals between sub-carrier signals are sufficiently large, theaccuracy of direction estimation can be stabilized due to the frequencydiversity effect.

Incidentally, the correlation matrix creating unit 22 may employ thecorrelation vector z shown in the formula 7 as well as the correlationmatrix R shown in the formula 3. In this case, the spatial profilecalculating unit 23 obtains direction-of-arrival estimation values bycalculating the spatial profile shown in the formula 8 as well as in theformula 4 for detecting a peak level. However, Vn,m represents the m-thelement of the correlation vector Vn.

$\begin{matrix}{z = {\sum\limits_{n = 1}^{Nc}{V_{n,1}*V_{n}}}} & (7) \\{{F(\theta)} = {{z^{H}{a(\theta)}}}^{2}} & (8)\end{matrix}$

Incidentally, when each sub-carrier signal is transmitted using amulti-carrier direct sequence code division multiple access (MC/DS-CDMA)method to be spread in the direction of time axis, the divided banddirection estimating unit 4 may be configured such that it takes outmulti-path signals in which the arrival time is different in asub-carrier signal and performs the direction estimation of the multiplepaths. An example of such configurations is illustrated in FIG. 4.

FIG. 4 is a diagram illustrating a different configuration of thedivided band direction estimating unit 4-1. In FIG. 4, the divided banddirection estimating unit 4 b is made up of a pilot signal creating unit20 for creating a known pilot signal embedded in each sub-carriersignal; a path search unit 30 for detecting a plurality of arrival pathtimings in each sub-carrier signal; a pilot signal correlationcalculating unit 31 for calculating cross correlation values between asub-carrier signals received by each of the detected multiple arrivalpath timings and a created pilot signal; a correlation matrix creatingunit 32 for creating a correlation matrix based on the pilot signalcorrelation values; and a spatial profile calculating unit 33 forcalculating a spatial profile that is spatial using the createdcorrelation matrix. The operation of the outline is described below withreference to FIG. 4. Incidentally, FIG. 4 shows an example when thenumber of antenna elements Na is 2 and the number of sub-carriers Nc inthe divided band is 2.

First, path search units 30-1 to 30-Ns create delay profiles using pilotsignals embedded in sub-carrier signals and detect a peak timing of theupper received power as a path timing. Herein, the number of receivingpath timings detected for the n-th sub-carrier signal of certainsub-carrier signals in a path search unit 30-n is specified as Ln.However, n is 1 to Nc. A pilot signal correlation value h nk(tj) in thej-th path timing tj for the n-th sub-carrier signal fn-k received by thek-th antenna element 1-k can be expressed as the formula 9. Herein, thepilot signal is specified as r(s). However, s is 1 to Np where Np is thenumber of symbols of the pilot signal.

$\begin{matrix}{{h_{nk}\left( t_{j} \right)} = {\sum\limits_{s = 1}^{N_{p}}{{f_{n - k}\left( {t_{j} + {{No} \cdot \left( {s - 1} \right)}} \right)}{r^{*}(s)}}}} & (9)\end{matrix}$

Incidentally, the delay profile is created using a method of 1)composing the absolute value or square of the pilot signal correlationvalue h nk(tj) obtained by each of the antenna elements 1-1 to 1-N foreach of the same timings or 2) creating multiple delay profiles bymultiplying the pilot correlation value h nk(tj) of the same timing bythe weight on which a directional beam is formed, then adding both andobtaining the absolute value or square, and moreover synthesizing them.Also, the delay profile can suppress the noise component by equalizingbetween a plurality of frames.

Next, the correlation matrix creating unit 32 calculates a correlationmatrix R shown in the formula 11 using the pilot correlation value hnk(tj) calculated in the pilot signal correlation calculating unit 31and the correlation vector Vn(tj) shown in the formula 10. However, n is1 to Ns, k is 1 to Na and H is a vector complex conjugate transpose.

$\begin{matrix}{{V_{n}\left( t_{j} \right)} = \begin{bmatrix}{h_{n,1}\left( t_{j} \right)} & {h_{n,2}\left( t_{j} \right)} & \ldots & {h_{n,{Na}}\left( t_{j} \right)}\end{bmatrix}^{T}} & (10) \\{R = {\sum\limits_{n = 1}^{Ns}{\sum\limits_{j = 1}^{Ln}{{V_{n}\left( t_{j} \right)} \cdot {V_{n}\left( t_{j} \right)}^{H}}}}} & (11)\end{matrix}$

Next, the spatial profile calculating unit 33 calculates the spatialprofile shown in the formula 4 to perform the direction estimation usingthe correlation matrix R created by the correlation matrix creating unit32.

Incidentally, the correlation matrix creating unit 32 synthesizes thecorrelation vector Vn(tj) and then calculates the spatial spectrum.However, the correlation matrix creating unit may calculate the spatialprofile for each path as shown in the formula 12 using the correlationvector Vn(tj) of each path. Incidentally, the formula 12 illustrates adirection estimation evaluation function of the j-th pass for the n-thsub-carrier signal. However, n is 1 to Ns and j is 1 to Ln.F _(nj)(θ)k=|a ^(H)(θ)V _(n)(t _(j))|²  (12)

Incidentally, the correlation matrix creating unit 32 may employ thecorrelation vector z shown in the formula 13 as well as the correlationmatrix R shown in the formula 11. In this case, the spatial profilecalculating unit 32 obtains the direction-of-arrival estimation valuesby calculating the spatial profile shown in the formula 14 as well as inthe formula 4 for detecting a peak level. Herein, Vn,m(tj) representsthe m-th element of the correlation vector Vn(tj).

$\begin{matrix}{z = {\sum\limits_{n = 1}^{Ns}{\sum\limits_{j = 1}^{Ln}{{V_{n,1}^{*}\left( t_{j} \right)} \cdot {V_{n}\left( t_{j} \right)}}}}} & (13) \\{{F(\theta)} = {{z^{H}{a(\theta)}}}^{2}} & (14)\end{matrix}$

Incidentally, in this embodiment, the divided band direction estimatingunit 4 performs the direction estimation using the beam former method.Eigenvalue analysis methods, such as the MUSIC method and ESPRIT methodwhose information is disclosed in “Adaptive Signal Processing by ArrayAntenna” (Science Press, Inc.) by Kikuma and a high resolution method ofa direction-of-arrival estimation such as the Capon Method including theinverse matrix operation of a correlation matrix, can apply to thecorrelation matrix R of the output of the correlation matrix creatingunit 22 or the correlation matrix creating unit 32 shown in the formula3 or the formula 11. When the number of sub-carrier signals Nc belongingto sub-carrier signals is smaller than the number of array elements,however, since the case can be considered where the number of ranks ofthe correlation matrix R that is the output of the correlation matrixcreating unit 22 does not reach the full rank, a direction estimationalgorithm needs to be properly selected in accordance with the number ofsub-carriers Nc. Or when the correlation matrix creating unit 32 isused, such an algorithm needs to be selected in accordance with thenumber that the number of sub-carrier signals Nc and the number of pathsLn are added. Furthermore, when the configuration of the array antenna 1is uniform linear array arrangement, the arrival direction estimationprocessing in a beam space in which a directional vector is put into areal number can be applied by multiplying the correlation matrix Robtained in the correlation matrix creating unit 22 or the correlationmatrix creating unit 32 by spatial smoothing processing or unitaryconversion processing for multiplying the unitary conversion matrix.

Incidentally, sub-carrier transmission may be sub-carrier signals towhich the orthogonal frequency division multiplexing (OFDM) is applied.In this case, frequency in which each sub-carrier signal is orthogonalin the OFDM symbol section is selected and used. Also, sub-carriertransmission can be applied to the code division multiplexed MC-CDMAmethod in the direction of the frequency axis. In this case, the sameeffect can be obtained by performing the operation explained in thisembodiment through the calculation of the pilot correlation value ofeach sub-carrier signal for each user using the pilot signal embedded inthe multiplexed sub-carrier signal for each individual user.

Multi-carrier transmission can also be applied to the code divisionmultiplexed MC/DS-CDMA method in the direction of time axis in the samemanner. In this case, the same effect can be obtained by performing theoperation explained in this embodiment through the calculation of thepilot correlation value of each sub-carrier signal for each user afterextracting a code division multiplexed user signal in the direction oftime axis of each sub-carrier signal by de-spreading.

Furthermore, when code division multiplexed users exist, the dividedband array weight creating unit 5 may be additionally given a beamcreating function for reducing interference between users who are codedivision multiplexed. This function can be realized by creating a weightof a receive array that has the main beam in the estimation direction ofthe divided band direction estimating unit 4 in each sub-carrier signalsin the direction of a desired user and forms a null in the direction ofother multiplexed users.

2nd Exemplary Embodiment

FIG. 5 is a block diagram illustrating a configuration of a transmittingunit of an adaptive antenna radio communication device according toEmbodiment 2 of the present invention. According to the configuration ofthis embodiment, the operation in the configuration of FIG. 1 explainedin Embodiment 1 is performed for creating a transmission directivity ineach sub-carrier based on the direction estimation result by eachdivided band direction estimating unit 4. Incidentally, since a blockdiagram until the direction estimation result of the divided banddirection estimating unit 4 is obtained is the same as that ofEmbodiment 1, the description is omitted here. In FIG. 5, an adaptiveantenna radio communication device is made up of a sub-carriertransmission weight creating unit 40 for creating a weight of atransmission array based on the estimation result of the divided banddirection estimating unit 4; a sub-carrier transmission directivitycreating unit 41 for multiplying each signal in which transmittingsub-carrier signals (f1 to fNs) are reproduced as much as the number oftransmission array elements by a weight of a transmission array; a mixer42 for mixing the weighted sub-carrier signals; a radio transmittingunit 43 for frequency-converting the output of the mixer 42 to the radiofrequency. Incidentally, an example of a configuration is illustrated inFIG. 5 when the number of antenna elements Na is 2, the number ofsub-carriers Ns is 2 and the number of divided bands Nd is 2. Theoperation of the outline is described below with reference to FIG. 5.

The operation until the divided band direction estimating units 4-1 to4-Nd estimate the direction-of-arrival in each divided band based on thehigh frequency signal s1 that is transmitted in the multi-carrier modereceived by the array antenna 1 is the same as that of Embodiment 1, thedescription is omitted here.

Next, the sub-carrier transmission weight creating unit 40 creates aweight of a transmission array based on the estimation results from Nddivided band direction estimating units 4. Creation of a transmissionarray weight operates differently according to a duplex system of aradio communication system. For example, the operation is differentaccording to a time division duplex (TDD) method or a frequency divisionduplex (FDD) method as described below.

In case of a TDD method, since transmit band and receive band are sharedby time division, a weight of a receive array created by each of thedivided band array weight creating units 5-1 to 5-Ndis used as a weightof a transmission array Ws based on the estimation direction results ofthe divided band direction estimating units 4-1 to 4-Nd of each dividedband. Also, when the spread (deviation) of the direction estimationresults of the divided band direction estimating units 4-1 to 4-N ineach divided band over the entire communication band is large, in aradio communication system in which a plurality of users exist accordingto the code division multiplexing, there is a problem in that multiuserinterference becomes larger. For this reason, any of the followingoperations is applied.

1) The divided band array weight creating units 5-1 to 5-Nd create thetransmission weight array Ws for creating a transmitting directionalbeam in the direction of estimation (maximum peak direction of spatialprofiles calculated respectively in the divided band directionestimating units 4-1 to 4-Nd for each divided band) giving the maximumreceived power among the entire divided bands from the estimationdirection results of the divided band direction estimating units 4-1 to4-Nd for each divided band.

2) The divided band array weight creating units 5-1 to 5-Nd calculatethe deviation of the estimation direction in the entire communicationband from the estimation direction results from the divided banddirection estimating units 4-1 to 4-Nd for each divided band. When thedeviation is smaller than the predetermined value, the divided bandarray weight creating units 5-1 to 5-Nd create the transmission arrayweight Ws facing toward the multiple main beams in the average directionof each estimation direction result of the divided band directionestimating units 4-1 to Nd for each divided band. Furthermore, when thedeviation is higher than the predetermined value, the divided band arrayweight creating units 5-1 to 5-Nd create it in the estimation direction(upper peak direction of spatial profiles calculated respectively in thedivided band direction estimating units 4-1 to 4-Nd for each dividedband) of upper received power among the entire divided bands.

In case of a FDD method, transmit band and receive band are different.However, any of the following operations is applied on the basis of theestimation values from each of the divided band direction estimatingunits 4-1 to 4-Nd.

1) The divided band array weight creating units 5-1 to 5-Nd create thetransmission weight array Ws for creating a transmitting directionalbeam in the direction of estimation (maximum peak direction of spatialprofiles calculated respectively in the divided band directionestimating units 4-1 to 4-Nd for each divided band) giving the maximumreceived power among the entire divided bands from the estimationdirection results of the divided band direction estimating units 4-1 to4-Nd for each divided band.

2) The divided band array weight creating units 5-1 to 5-Nd calculatethe deviation of the estimation direction in the entire communicationband from the estimation direction results from the divided banddirection estimating units 4-1 to 4-Nd for each divided band. When thedeviation is smaller than the predetermined value, the divided bandarray weight creating units 5-1 to 5-Nd create the transmission arrayweight Ws facing toward the multiple main beams in the average directionof each estimation direction result of the divided band directionestimating units 4-1 to Nd for each divided band. Furthermore, when thedeviation is higher than the predetermined value, the divided band arrayweight creating units 5-1 to 5-Nd create it in the estimation direction(upper peak direction of spatial profiles calculated respectively in thedivided band direction estimating units 4-1 to 4-Nd for each dividedband) of upper received power among the entire divided bands.

Next, transmitting data is modulated at a modulator that is notillustrated in a predetermined modulation format and transmittingsub-carrier signals 41-1 to Ns are created. The sub-carrier transmissiondirectivity creating unit 41-1 to 41-Ns divides the transmittingsub-carrier signals 41-1 to 41-Ns to the number equal to the number ofelements in the array antenna 1 Na for multiplying each of them byelements in the transmission array weight Ws=[w1, w2, . . . , wna]created in the sub-carrier transmission weight creating unit 40, andoutputs them to the mixers 42-1 to 42-Na.

The mixers 42-1 to 42-Na mix output signals corresponding to the numberof array elements in the directivity-weighted sub-carrier transmissiondirectivity creating units 41-1 to 41-Ns such that sub-carrier signalsare arranged at assigned frequency intervals respectively. The radiotransmitting units 43-1 to 43-Na transmit outputs of the mixers 42-1 to42-Na at each radio frequency from the antenna elements 44-1 to 44-Naconfiguring the frequency-converted array antenna 44.

As described above, according to this embodiment, in addition to theeffect of Embodiment 1, as a directivity is transmitted in theestimation directions of the divided band direction estimating units 4-1to 4-Nd, multi-path interference can be reduced and communicationquality can be improved. Also, by restricting the direction ofestimation giving the maximum received power among all divided bands orthe directivity transmitting direction in the direction having higherreceived power among divided bands according to the deviation of thedirection estimation values of each divided band in the entirecommunication band, a directivity can be transmitted with betterefficiency such that multiuser interference is suppressed. Thus,multiuser interference can be suppressed and the system capacity can beimproved.

Incidentally, sub-carrier transmission which can be used for sending maybe sub-carrier signals to which orthogonal frequency divisionmultiplexing (OFDM) is applied. In this case, frequency in which eachsub-carrier signal is orthogonal in the OFDM symbol section is selectedand used. Sub-carrier transmission can also be applied to the codedivision multiplexed MC-CDMA method in the direction of the frequencyaxis and each user can obtain the same effect by performing theoperation explained in this embodiment. Also, it can be adapted to thecode division multiplexed MC/DS-CDMA method in the direction of the timeaxis in the same manner. In this case, each user can obtain the sameeffect by performing the operation explained in this embodiment, too.

Furthermore, when code division multiplexed users exist, the sub-carriertransmission weight creating unit 40 may be additionally given a beamcreating function for reducing interference between users who are codedivision multiplexed in the same manner as in Embodimentl.

3rd Exemplary Embodiment

FIG. 6 is a block diagram illustrating a configuration of the receivingunit of an adaptive antenna radio communication device according toEmbodiment 3 of the present invention. The configuration of the presentembodiment, in the configuration of FIG. 1 explained in Embodiment 1,further comprises an entire band direction estimating unit 50 forestimating the direction in the entire communication band and adirection estimation result selecting unit 51 by using all sub-carriersignals receiving by the array antenna 1. The direction estimationresult selecting unit 51 detects an angle spread by using a spatialprofile to be calculated in the entire band direction estimating unit50, selects and outputs the direction estimation result from either ofthe entire band direction estimating unit 50 or the divided banddirection estimating unit 4. Incidentally, since a block diagram untilthe direction estimation result of the divided band direction estimatingunit 4 is obtained is the same as that of Embodiment 1, the descriptionis omitted here. The part that is different from Embodiment 1 is mainlydescribed below with reference to FIG. 6. Incidentally, FIG. 6illustrates an example when the number of antenna elements Na is 2, thenumber of sub-carriers Ns is 2 and the number of divided bands Nd is 2.

The operation until the divided band direction estimating units 4-1 to4-Nd estimate the direction-of-arrival in each divided band based on thehigh frequency signal s1 that is transmitted in the multi-carrier modereceived by the array antenna 1 is the same as Embodiment 1, thedescription is omitted here.

The entire band direction estimating unit 50 is to input therein Rncalculated in all divided bands 3-1 to 3-Nd when the correlation matrixR shown in the formula 3 calculated in the n-th divided band 3-n isspecified as Rn (however, n is 1 to Nd) and calculates a compositesummation Ra of the correlation matrix Rn shown in the formula 15. Forexample, a spatial profile according to the Fourier method shown in theformula 16 is calculated by varying θ in a predetermined angle step Δθand the peak direction having the predetermined number M (M□1) in thedescending order of the peak level of a spatial profile is detected andthen average direction-of-arrival estimation of sub-carrier signals inthe entire communication band is performed. However, a(θ) is adirectional vector that depends on the element arrangement of the arrayantenna 1. For example, it can be expressed as the formula 5 for anuniform linear array having an element space d. Herein, λ is awavelength of a carrier band, and θ specifies the normal direction ofthe array as the direction of 0°. Furthermore, H is a complex conjugatetranspose.

$\begin{matrix}{R_{a} = {\sum\limits_{n = 1}^{Nd}R_{n}}} & (15) \\{{F(\theta)} = {{a(\theta)}^{H}R_{a}{a(\theta)}}} & (16)\end{matrix}$

Next, the direction estimation result selecting unit 51 calculates anangle spread AS using the direction estimation value φkm of all dividedband direction estimating units 4-1 to 4-Nd and spatial profile value(or the direction-of-arrival estimation evaluation function value)Fm(φm) in each of divided bands 3-m by applying the formula shown in theformula 17. Herein, m represents 1 to Nd. Also, φ0 is given by theformula 18, and φkm indicates the direction-of-arrival of the k-th pathamong the total Lm paths detected by the divided band directionestimating unit 4-m in the m-th divided band 3-m. When the angle spreadAs is less than the predetermined value K, the direction estimationresult selecting unit 51 selects the estimation values of the entireband direction estimating unit 50 using the angle spread As calculatedand outputs them to all divided band array weight creating units 5-1 to5-Nd in common. On the other hand, when the angle spread AS is greaterthan the predetermined value K, the direction estimation resultselecting unit 51 outputs the estimation value of the divided banddirection estimating unit 4-m in the m-th divided band 3-m to thedivided band array weight creating unit 5-m in the same manner as inEmbodiment 1. Herein, m represents 1 to Nd.

Furthermore, as a different method for calculating the angle spread AS,the angle spread AS may be obtained from the formula 17 using only thedirection estimation value φkm giving the upper spatial profile value(or the direction-of-arrival estimation evaluation function value)Fm(φkm).

$\begin{matrix}{{AS} = \sqrt{\frac{\sum\limits_{m = 1}^{Nd}{\sum\limits_{k = 1}^{Lm}{\left( {\phi_{km} - \phi_{0}} \right)^{2}{F_{m}\left( \phi_{km} \right)}}}}{\sum\limits_{m = 1}^{Nd}{\sum\limits_{k = 1}^{Lm}{F_{m}\left( \phi_{km} \right)}}}}} & (17) \\{\phi_{0} = \frac{\sum\limits_{m = 1}^{Nd}{\sum\limits_{k = 1}^{Lm}{\phi_{km}{F_{m}\left( \phi_{km} \right)}}}}{\sum\limits_{m = 1}^{Nd}{\sum\limits_{k = 1}^{Lm}{F_{m}\left( \phi_{km} \right)}}}} & (18)\end{matrix}$

Then, the divided band array weight creating unit 5 creates a weight ofa receive array facing toward the main beam direction in a particulardirection according to the selected direction estimation result by thedirection estimation result selecting unit 51, and outputs it to thesub-carrier directivity creating unit 6. The sub-carrier directivitycreating unit 6 outputs signals by multiplication-combining commonlyeach sub-carrier signal by the created receive array weight. Namely, thedivided band array weight creating unit 5-m in the m-th divided band 3-mcreates a weight of a receive array facing toward the main beamdirection in a particular direction for sub-carrier signals belonging tothem-th divided band 4-m, according to the selected direction estimationresult by the direction estimation result selecting unit 51. Thesub-carrier directivity creating unit 6-m outputs signals bymultiplication-combining commonly each sub-carrier signal by the createdreceive array weight. This operation is performed for all m, i.e., from1 to Nd.

The demodulating unit 7 receives data, performing demodulation operationusing each sub-carrier signal in which a directivity is received.

As described above, according to this embodiment, in addition to theeffect of Embodiment 1, since the direction estimation result selectingunit 51 detects an angle spread of a sub-carrier signal in the entirecommunication band, directivity formation different with the respectiveentire divided bands or directivity formation common to all dividedbands 3 can be switched in accordance with the angle spread AS. Thus,when the angle spread AS is small, the average direction-of-arrival forall sub-carrier signals can be estimated. For this reason, by frequencyselective fading, even when the receiving level of some bands is small,robust direction-of-arrival estimation can be made in the wholecommunication band.

Incidentally, detection of an angle spread by the direction estimationresult selecting unit 51 is calculated on the basis of the spread of thedirection-of-arrival estimation value in each divided band. However, theangle spread is also detected by applying a method based on a spatialprofile to be calculated in the entire band direction estimating unit50. As a method for calculating an angle spread from the spatialprofile, information is described, for example, in “ConcurrentEstimation of Direction-of-Arrival and Angle Spread using MUSICAlgorithm” by N. S. M. Shah et al., 2000 IEICE (The Institute ofElectronics, Information and Communication Engineers) CommunicationSociety Conference, B-1-31. By obtaining a spatial profile from thecorrelation matrix Ra calculated in the formula 15 and using the anglespread AS calculated form the spatial profile, as described above, theestimation results from the entire band direction estimating unit 50 ordivided band direction estimating units 4-1 to 4-Nd can be selectivelyswitched.

Incidentally, in this embodiment, the entire band direction estimatingunit 50 performs the direction estimation using sub-carrier signals ofthe entire communication band. In addition, a configuration to performthe direction estimation with the number of divisions greater than thenumber of sub-carrier signal divisions Ns used by the divided banddirection estimating unit 4 may be good.

Incidentally, the entire divided band direction estimating unit 50 inthis embodiment performs the direction estimation using the beam formermethod. Eigenvalue analysis methods, such as the MUSIC and ESPRITmethods whose information is disclosed in “Adaptive Signal Processing inArray Antennas” (Kikuma, Science Press, Inc.) and a high resolutionmethod of a direction-of-arrival estimation, such as the Capon Methodincluding the inverse matrix operation of a correlation matrix, canapply to the correlation matrix Ra shown in the formula 15. When thenumber of sub-carrier signals Nc belonging to the divided band 3 or thenumber of paths is smaller than the number of array elements, however,since the case can be considered where the number of ranks of thecorrelation matrix that is the output of the correlation matrix creatingunit 22 does not reach the full rank, a beam former method can beconsidered to be adaptively used together according to the number ofranks or the number of paths. Furthermore, when the configuration of thearray antenna 1 is uniform linear array arrangement, the arrivaldirection estimation processing in a beam space in which a directionalvector is put into a real number can be applied in the same manner bymultiplying the correlation matrix Ra shown in the formula 15 by thespatial smoothing processing and unitary conversion processing formultiplying the unitary conversion matrix.

Incidentally, sub-carrier transmission may be sub-carrier signals towhich the orthogonal frequency division multiplexing (OFDM) is applied.In this case, frequency in which each sub-carrier signal is orthogonalin the OFDM symbol section is selected and used. Also, sub-carriertransmission can be applied to the code division multiplexed MC-CDMAmethod in the direction of the frequency axis. In this case, the pilotcorrelation value of each sub-carrier signal for each user is calculatedby using the pilot signal embedded in the multiplexed sub-carriersignals for each individual user. Accordingly, the same effect can beobtained by performing the operation explained in the embodiment.

Also, it can be adapted even to the code division multiplexed MC/DS-CDMAmethod in the direction of the time axis in the same manner. In thiscase, a user signal that is code division multiplexed in the directionof time axis of each sub-carrier signal is extracted by de-spreading.And then, a pilot correlation value of each sub-carrier signal for eachuser is calculated. Thus, the same effect can be obtained by performingthe operation explained in this embodiment.

Furthermore, when code division multiplexed users exist, the dividedband array weight creating unit 5 may be additionally given a beamcreating function for reducing interference between users who are codedivision multiplexed.

4th Exemplary Embodiment

FIG. 7 is a block diagram illustrating a configuration of a transmittingunit of an adaptive antenna radio communication device according toEmbodiment 4 of the present invention. The configuration of thisembodiment, in the configuration of FIG. 5 explained in Embodiment 2,further comprises an entire band direction estimating unit 50 and adirection estimation result selecting unit 51. Incidentally, since ablock diagram until the direction estimation result of the divided banddirection estimating unit 4 is obtained is the same as that ofEmbodiment 1, the description is omitted here. The part that isdifferent from Embodiment 1 is mainly described below with reference toFIG. 7. Incidentally, FIG. 7 illustrates an example when the number ofantenna elements Na is 2, the number of sub-carriers Ns is 2 and thenumber of divided bands Nd is 2.

The operation until the divided band direction estimating units 4-1 to4-Nd estimate the direction-of-arrival in each divided band based on thehigh frequency signal s1 that is transmitted in the multi-carrier modereceived by the array antenna 1 is the same as Embodiment 1, thedescription is omitted here.

The entire band direction estimating unit 50 operates in the same manneras in Embodiment 3.

The direction estimation result selecting unit 51 selects the estimationvalue of the entire band direction estimating unit 50 using the anglespread AS that is calculated in the same manner as in Embodiment 3 andoutputs it to the sub-carrier transmission weight creating unit 40, whenthe angle spread AS is smaller than the predetermined value K. On theother hand, when the angle spread As is greater than the predeterminedvalue K, the direction estimation result selecting unit 51 outputs theestimation values of the divided band direction estimating units 4-1 to4-Nd in each of divided bands 3-1 to 3-Nd to the sub-carriertransmission weight creating unit 40 in the same manner as in Embodiment2. Herein, m is 1 to Nd.

Furthermore, as a different method for calculating the angle spread AS,the angle spread AS may be obtained from the formula 17 using only thedirection estimation value φkm giving the upper spatial profile value(or the direction-of-arrival estimation evaluation function value)Fm(Φkm).

Next, the sub-carrier transmission weight creating unit 40 creates aweight of a transmission array based on the output of the directionestimation result selecting unit 51. The sub-carrier transmission weightcreating unit 40 is to input the estimation values of the divided banddirection estimating units 4-1 to 4-Nd in each of divided bands 3-1 to3-Nd, when the angle spread AS is greater than the predetermined value Kand to perform the same operation as the sub-carrier transmission weightcreating unit 40 in a mode of Embodiment 2. On the other hand, when theangle spread AS is less than the predetermined value, since thesub-carrier transmission weight creating unit 40 is to select and inputthe estimation value of the entire band direction estimating unit 50, itcreates a weight of a transmission array facing toward the main beam inthe direction of the direction estimation value.

Then, transmitting data is modulated at a modulator that is notillustrated in a predetermined modulation format and the transmittingsub-carrier signals 41-1 to 41-Ns are created. The sub-carriertransmission directivity creating unit 41-1 to Ns divides thetransmitting sub-carrier signals 41-1 to 41-Ns to the number equal tothe number of elements of array antenna 1 Na for multiplying each ofthem by elements in the transmission array weight Ws=[w1, w2, . . . ,wna] and outputs it to the mixers 42-1 to 42-Na.

The following operation is the same as that of Embodiment 2.

As described above, according to this embodiment, in addition to theeffects of Embodiment 1 and Embodiment 2, directivity formationdifferent with the respective entire divided bands or transmissiondirectivity formation common to all divided bands 3 can be switched inaccordance with the angle spread AS. Thus, when the angle spread AS issmall, the average direction-of-arrival for all sub-carrier signals canbe estimated. For this reason, by frequency selective fading, even whenthe receiving level of some bands is small, robust direction-of-arrivalestimation can be made in the whole communication band. Since thedirectivity transmission using the result ensures more stabilizedoperation, multiuser interference can be suppressed and the systemcapacity can be improved.

Incidentally, in this embodiment, the entire band direction estimatingunit 50 performs the direction estimation using sub-carrier signals ofthe entire communication band. However, a configuration to perform thedirection estimation with the number of divisions greater than thenumber of sub-carrier signal divisions Ns used by the divided banddirection estimating unit 4 may be good.

Incidentally, sub-carrier transmission may be sub-carrier signals towhich the orthogonal frequency division multiplexing (OFDM) is applied.In this case, frequency in which each sub-carrier is orthogonal in theOFDM symbol section is selected and used. Also, sub-carrier transmissioncan be applied to the code division spread MC-CDMA mode in the directionof the frequency axis. In this case, the operation explained in thisembodiment is performed after user signals are extracted for each codedivision multiplexed user following de-spreading of spread codes.

Also, code multiplexed MC-DS-CDMA mode in the direction of time axis canbe adapted in the same manner. In this case, the operation explained inthis embodiment is performed after user signals are extracted for eachcode division multiplexed user following de-spreading of spread codes.

Furthermore, when code division multiplexed users exist, the sub-carriertransmission weight creating unit 40 may be additionally given a beamcreating function for reducing interference between users who are codedivision multiplexed in the same manner as in Embodiment 1.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful for an adaptiveantenna radio communication device and suitable for multi-carriertransmission.

What is claimed:
 1. A device for estimating a direction-of-arrival of aradio wave including a plurality of high frequency signals, the devicecomprising: an array antenna including a plurality of antenna elementsfor receiving the high frequency signals; a demultiplexer fordemultiplexing the received high frequency signal for each of theplurality of antenna elements to generate at least four frequencycomponent signals divided into at least two divided bands; and adirection estimating unit for estimating the direction-of-arrival of theradio wave by using the frequency component signals in one of the atleast two divided bands independent of the other frequency componentsignals in the other of the at least two divided bands, the directionestimating unit including: at least two correlation units forcalculating at least two correlation values based on the frequencycomponent signals in the one divided band respectively, a correlationmatrix unit for calculating a correlation matrix based on the at leasttwo correlation values, and a spatial profile unit for estimating thedirection-of-arrival of the radio wave based on the correlation matrix.2. A device for estimating a direction-of-arrival of a radio waveincluding a plurality of high frequency signals, the device comprising:an array antenna including a plurality of antenna elements for receivingthe high frequency signals; a demultiplexer for demultiplexing thereceived high frequency signal for each of the plurality of antennaelements to generate at least four frequency component signals dividedinto Nd divided bands (Nd : integer of two or more); and a directionestimating unit for estimating the direction-of-arrival of the radiowave, for at least one of the Nd divided bands, by using the frequencycomponent signals in one of the bands independent of the other frequencycomponent signals in the other of the bands the direction estimatingunit including: at least two correlation units for calculating at leasttwo correlation values based on the frequency component signals in theone divided band respectively, a correlation matrix unit for calculatinga correlation matrix based on the at least two correlation values, and aspatial profile unit for estimating the direction-of-arrival of theradio wave based on the correlation matrix.
 3. The device for estimatingthe direction-of-arrival of the radio wave of claim 1, wherein thedirection estimating unit calculates a pilot signal correlation valuewith each of the inputted frequency component signals by using a knownpilot signal embedded in each of the two or more of the plurality offrequency component signals, calculates the pilot signal correlationvalue on each of the two or more of the plurality of frequency componentsignals in the high frequency signals received by different antennaelements and estimates the direction-of-arrival based on calculated aplurality of the pilot signal correlation values.
 4. The device forestimating the direction-of-arrival of the radio wave of claim 1,wherein the direction estimating unit calculates a pilot signalcorrelation value with each of the inputted frequency component signalsby using a known pilot signal embedded in each of the two or more of theplurality of frequency component signals, calculates the pilot signalcorrelation value on each of the two or more of the plurality offrequency components signals in the high frequency signals received bydifferent antenna elements and estimates the direction-of-arrival bygenerating a correlation matrix from calculated a plurality of the pilotsignal correlation values.
 5. The device for estimating thedirection-of-arrival of the radio wave of claim 4, wherein L frequencycomponent signals (L : integer of two or more) belong to each of thedivided bands, and the direction estimating unit estimates thedirection-of arrival for each of the divided bands by using thecorrelation matrix R which is represented as R=V₁V₁ ^(H)+V₂V₂^(H)+···+V_(L)V_(L) ^(H) (Vk is a column vector having a pilot signalcorrelation value as an m-th element in the m-th antenna element withrespect to the k-th frequency component signal (k is positive integerequal to or less than L); and H is a complex conjugate transposedoperator).
 6. The device for estimating the direction-of-arrival of theradio wave of claim 4, wherein L frequency component signals (L :integer of two or more) belong to each of the divided bands, and thedirection estimating unit estimates the direction-of-arrival for each ofthe divided bands by using the correlation matrix Z which is representedas z=V_(1x) ^(*)V₁+V_(2x) ^(*)V₂+···+V_(Lx) ^(*)V_(N) (where Vk is acolumn vector having a pilot signal correlation value as an m-th elementin the m-th antenna element with respect to the k-th frequency componentsignal(k is positive integer equal to or less than L); Vkx is an x-thelement of the column vector Vk (x is a positive integer equal to orless than the number of antenna elements); and * is a complex conjugateoperator).
 7. The device for estimating the direction-of-arrival of theradio wave of claim 1, wherein the direction estimating unit calculatesa delay profile by mutual correlation calculation with each of the twoor more of the plurality of frequency component signals by using a knownpilot signal embedded in each of the two ore more of the plurality offrequency component signals, detects a plurality of pathdirection-of-arrival timings based on the delay profile and estimatesthe direction-of-arrival based on the plurality of correlation matrixcalculated from each of the plurality of frequency component signalsreceived by the different antenna elements on each of the plurality ofpath direction-of-arrival timings.
 8. The device for estimating thedirection-of-arrival of the radio wave of claim 7, wherein L frequencycomponent signals (L : integer of two or more) belong to each of thedivided bands, and the direction estimating unit estimates thedirection-of-arrival for each of the divided bands by using thecorrelation matrix R which is represented as of (equation 1)$R = {\sum\limits_{k = 1}^{L}{\sum\limits_{p = 1}^{S}{{V_{k}(p)}{V_{k}(p)}^{H}}}}$(Vk(p) is a column vector having the pilot signal correlation values asan m-th element in the m-th antenna element of the p-th arrival path(the number of whole arrival paths is specified as S) with respect tothe k-th frequency component signal(k is positive integer equal to orless than L) and H is a complex conjugate transposed operator).
 9. Thedevice for estimating the direction-of-arrival of the radio wave ofclaim 7, wherein L frequency component signals (L : integer of two ormore) belong to each of the divided bands, and the direction estimatingunit estimates the direction-of-arrival for each of the divided bands byusing the correlation matrix Z which is represented as of (equation 2)$z = {\sum\limits_{k = 1}^{L}{\sum\limits_{p = 1}^{S}{{V_{kx}^{*}(p)}{V_{k}(p)}}}}$(Vk(p) is a column vector having the pilot signal correlation values asan m-th element in the m-th antenna element of the p-th arrival path(the number of whole arrival paths is specified as S) with respect tothe k-th frequency component signal(k is positive integer equal to orless than L); Vkx(p) is x-th element of the column vector Vk(p)(x is apositive integer equal to or less than the number of antenna elements);and H is a complex conjugate transposed operator).
 10. The device forestimating the direction-of-arrival of the radio wave of claim 5,wherein the direction estimating unit estimates the direction-of-arrivalby using the correlation matrix R and by using one of MUSIC method,ESPRIT method, CAPON method and Fourier method.
 11. The device forestimating the direction-of-arrival of the radio wave of claim 5,wherein the direction estimating unit estimates the direction-of-arrivalby applying a space smoothing process to the correlation matrix R andusing one of MUSIC method, ESPRIT method, CAPON method and Fouriermethod.
 12. The device for estimating the direction-of-arrival of theradio wave of claim 5, wherein the direction estimating unit estimatesthe direction-of-arrival by applying a unitary transformation process tothe correlation matrix R and using one method of MUSIC method, ESPRITmethod, CAPON method and Fourier method.
 13. The device for estimatingthe direction-of-arrival of the radio wave of claim 1, wherein thedemultiplexer demultiplexes the high frequency signal to a plurality offrequency component signals by using a Fourier transformation.
 14. Amethod for estimating a direction-of-arrival of a radio wave, the methodcomprising: receiving a plurality of high frequency signals included inthe radio wave by using an array antenna including a plurality ofantenna elements; generating at least four frequency component signalsby demultiplexing the received high frequency signals for each of theplurality of antenna elements to generate a plurality of frequencycomponent signals belonging to a at least two divided bands; andestimating the direction-of-arrival of the radio wave by using thefrequency component signals in one of the at least two divided bandsindependent of the other frequency component signals in the other of theat least two divided bands, the estimating step including: calculatingat least two correlation values based on the frequency component signalsin the one divided band respectively, calculating a correlation matrixbased on the at least two correlation values, and estimating thedirection-of-arrival of the radio wave based on the correlation matrix.15. A method for estimating a direction-of-arrival of a radio waveincluding a plurality of high frequency signals, the method comprising:receiving the high frequency signals by using an array antenna includinga plurality of antenna elements; generating a plurality of frequencycomponent signals by demultiplexing the received high frequency signalsfor each of the plurality of antenna elements to generate at least fourfrequency component signals; dividing the plurality of frequencycomponent signals into Nd divided bands (Nd : integer of two or more);and estimating the direction-of-arrival of the radio wave, for at leastone of the Nd divided bands by using the frequency component signals inone of the Nd divided bands independent of the other frequency componentsignals in any other of the Nd divided bands, the estimating stepincluding: calculating at least two correlation values based on thefrequency component signals in the one divided band respectively,calculating a correlation matrix based on the at least two correlationvalues, and estimating the direction-of-arrival of the radio wave basedon the correlation matrix.
 16. The method for estimating thedirection-of-arrival of the radio wave of claim 14, the method furthercomprising: calculating a pilot signal correlation value with each ofthe inputted frequency component signals by using a known pilot signalembedded in each of the two or more of the plurality of frequencycomponent signals; calculating the pilot signal correlation value oneach of the two or more of the plurality of frequency component signalsin the high frequency signals received by different antenna elements;and estimating the direction-of-arrival based on calculated a pluralityof the pilot signal correlation values.
 17. The method for estimatingthe direction-of-arrival of the radio wave of claim 14, the methodfurther comprising: calculating a pilot signal correlation value witheach of the inputted frequency component signals by using a known pilotsignal embedded in each of the two or more of the plurality of frequencycomponent signals; calculating the pilot signal correlation value oneach of the two or more of the plurality of frequency components signalsin the high frequency signals received by different antenna elements;and estimating the direction-of-arrival by generating a correlationmatrix from calculated a plurality of the pilot signal correlationvalues.
 18. The method for estimating the direction-of-arrival of theradio wave of claim 14, the method further comprising: calculating adelay profile by mutual correlation calculation with each of the two ormore of the plurality of frequency component signals by using a knownpilot signal embedded in each of the two or more of the plurality offrequency component signals; detecting a plurality of pathdirection-of-arrival timings based on the delay profile; and estimatingthe direction-of-arrival based on the plurality of correlation matrixcalculated from each of the plurality of frequency component signalsreceived by the different antenna elements on each of the plurality ofpath direction-of-arrival timings.
 19. The method for estimating thedirection-of-arrival of the radio wave of claim 14, wherein thedemultiplexing includes demultiplexing the high frequency signal to aplurality of frequency component signals by using a Fouriertransformation.